Most LCDs are locked to 60Hz. There has been some that thought higher was better (maybe to teen age fighter pilots) but more Hz is needed for 3D (240 is that number.)
If it goes 60Hz then it's likely to be doing what it is supposed to do.
I have a problem regarding the Samsung 2233rz monitor and I think it's a big one. My issue came when I tried connecting my 2233rz to my laptop. I recently bought a DVI-HDMI cable(DVI has Dual Link) and when I started Windows to change the refresh rate, all the resolution where blocked at 60Hz. My laptop has a Nvidia GT 320M video card with a VGA and HDMI slot, so I really don't think that's the problem. When I connected my CRT monitor through my laptop's VGA slot everything was OK, I even managed a 120hz with that old CRT monitor. Currently my 2233rz is connected via a DVI-HDMI cable. I don't think this is possible with such a expensive monitor and I really need a help.
My operating system is Windows 7 64-bit.